Control method and control system for power converter, and power converter and chip

Abstract

The present disclosure relates to the technical field of circuit control, and specifically relates to a control method and control system for a power converter, and a power converter and a chip. The control method comprises: periodically acquiring a real-time power grid voltage on the basis of a first preset duration; if an acquired first real-time power grid voltage is not within a preset voltage threshold range, controlling a power converter to enter a wave-blocking standby state from a normal power generation state; when the power converter is in the wave-blocking standby state, acquiring a duration within which the real-time power grid voltage is within the voltage threshold range; and when the duration is not less than a second preset duration, controlling the power converter to enter the normal power generation state. By means of the control method for a power converter, when a sudden change occurs in a power grid voltage, a rapid response can be made to trigger the wave-blocking protection of the power converter, and the operating efficiency of the power converter in the case of minor fluctuations in the power grid can be ensured.

Description

Control method, control system, power converter and chip of power converter

[0001] Related applications

[0002] The present disclosure claims priority to the Chinese patent application No. 2024113397126, filed on September 24, 2024, entitled "Control method, control system, power converter and chip of power converter", the contents of which are hereby incorporated by reference in their entirety. TECHNICAL FIELD

[0003] The present disclosure relates to the technical field of circuit control, and particularly relates to a control method, a control system, a power converter and a chip of a power converter. BACKGROUND

[0004] With the development of renewable energy technologies, photovoltaic power generation systems and other power systems have been widely used. In these systems, power converters serve as an important device to convert different forms of electrical energy (such as direct current) into alternating current or direct current that meets the requirements of the target system, and then connect it to the power grid or other loads. Precise control of the power converter is crucial to ensure efficient and stable delivery of electrical energy to the power grid.

[0005] However, in the operation of the power grid, due to fluctuations or sudden changes in the voltage and frequency of the power grid, especially in the case of sudden disconnection or temporary fluctuations of the power grid, the operation of the power converter will be severely affected. In this case, traditional grid protection mechanisms (such as under-voltage and under-frequency protection) are difficult to respond in such a short time, resulting in the power converter being unable to adjust the control strategy in time, thereby causing risks such as loss of phase lock, control disorder, and even device overcurrent damage.

[0006] Therefore, how to effectively protect the power converter when the power grid is abnormally fluctuating has become a problem to be solved in the current technical field of circuit control. SUMMARY

[0007] Therefore, it is necessary to provide a control method, a control system, a power converter and a chip of a power converter to solve the above technical problems.

[0008] In a first aspect, the present disclosure provides a control method of a power converter. The control method comprises:

[0009] periodically acquiring a real-time voltage of the power grid according to a first preset time period;

[0010] if the acquired first real-time voltage of the power grid is not within a preset voltage threshold range, controlling the power converter to enter a grid-blocking standby state from a normal power generation state;

[0011] When the power converter is in the blocking standby state, a duration in which the real-time voltage of the power grid is within the voltage threshold range is obtained;

[0012] When the duration is not less than the second preset duration, the power converter is controlled to enter the normal power generation state.

[0013] In one of the embodiments, the control method is applied to a control system of the power converter, and the control system at least includes a main controller and a CPLD;

[0014] The control method is implemented by the main controller;

[0015] The CPLD is used to enter the wave emitting state or the wave blocking state in response to the control instruction of the main controller, so that the power converter enters the normal power generation state or the blocking standby state.

[0016] In one of the embodiments, the first preset duration is determined by the maximum interrupt frequency of the main controller.

[0017] In one of the embodiments, the second preset duration is determined by the grid frequency.

[0018] In one of the embodiments, the second preset duration is greater than one time of the AC cycle duration of the power grid and less than two times of the AC cycle duration of the power grid.

[0019] In one of the embodiments, the control method further includes:

[0020] If the duration in which the power converter continuously stays in the blocking standby state is greater than a third preset duration, the power converter enters a shutdown state.

[0021] In one of the embodiments, after the real-time voltage of the power grid is periodically obtained according to the first preset duration, the control method further includes:

[0022] The voltage threshold range corresponding to the current AC cycle of the power grid is determined according to the real-time voltage of the power grid obtained in the historical AC cycle of the power grid.

[0023] In one of the embodiments, the voltage threshold range corresponding to the current AC cycle of the power grid includes voltage threshold ranges corresponding to each time point in the current AC cycle of the power grid;

[0024] The voltage threshold range corresponding to each time point is a voltage interval with a preset voltage difference, and the middle value of the voltage interval is obtained from the real-time voltage of the power grid in the N historical AC cycles of the power grid.

[0025] In one of the embodiments, the power conversion circuit in the power converter adopts an isolation type power conversion circuit including a resonance circuit.

[0026] In one of the embodiments, the isolated power conversion circuit is a single-stage isolated power conversion circuit or a 1.5-stage isolated power conversion circuit or a two-stage isolated power conversion circuit.

[0027] In a second aspect, the disclosure further provides a control system of a power converter. The control system comprises a main controller configured to:

[0028] periodically acquire a real-time grid voltage according to a first preset time period;

[0029] if the acquired first real-time grid voltage is not within a preset voltage threshold range, control the power converter to enter a blocking standby state from a normal power generation state;

[0030] when the power converter is in the blocking standby state, acquire a duration that the real-time grid voltage is within the voltage threshold range;

[0031] when the duration is not less than a second preset time period, control the power converter to enter the normal power generation state.

[0032] In one of the embodiments, the control system further comprises a CPLD, and the main controller is configured to:

[0033] if the acquired first real-time grid voltage is not within a preset voltage threshold range, control the CPLD to enter a blocking state from a wave generation state;

[0034] when the CPLD is in the blocking state, acquire a duration that the real-time grid voltage is within the voltage threshold range;

[0035] when the duration is not less than a second preset time period, control the CPLD to enter the wave generation state.

[0036] In a third aspect, the disclosure further provides a power converter comprising the control system of the second aspect.

[0037] In one of the embodiments, the power conversion circuit in the power converter adopts an isolated power conversion circuit comprising a resonant circuit.

[0038] In one of the embodiments, the isolated power conversion circuit is a single-stage isolated power conversion circuit or a 1.5-stage isolated power conversion circuit or a two-stage isolated power conversion circuit.

[0039] In a fourth aspect, the disclosure further provides a chip comprising a memory and a processor, the memory storing a computer program, and the processor implementing the steps of the method provided in the first aspect when executing the computer program.

[0040] The control method of the power converter disclosed in the present disclosure periodically samples the real-time voltage of the power grid, when the real-time voltage of the power grid is abnormal, controls the power converter to enter the wave blocking standby state, and when the real-time voltage of the power grid returns to normal and lasts for a period of time, controls the power converter to enter the normal power generation state. In this way, by periodically sampling the voltage of the power grid, real-time monitoring of the change of the voltage of the power grid is realized, so that the power converter can be switched to the standby state in time under abnormal conditions of the power grid, and the risk of damage to components can be avoided. Reduce; and through the mechanism of continuous monitoring and timing, after the power grid returns to normal, the power converter can restore power generation in time, improve energy utilization efficiency, and also avoid frequent switching of the power converter due to short-term fluctuations of the power grid. Working state, helps to prolong the service life of the equipment. BRIEF DESCRIPTION OF DRAWINGS

[0041] In order to more clearly illustrate the technical solutions in the embodiments of the present disclosure or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present disclosure, and those skilled in the art can also obtain other drawings according to the disclosed drawings without creative labor.

[0042] FIG. 1 is a schematic diagram of a single-stage isolated power conversion circuit topology in one embodiment;

[0043] FIG. 2 is a schematic diagram of a 1.5-stage isolated power conversion circuit topology in one embodiment;

[0044] FIG. 3 is a schematic diagram of the control method of the power converter in one embodiment;

[0045] FIG. 4 is a schematic diagram of the structure of the control system of the power converter in one embodiment;

[0046] FIG. 5 is a schematic diagram of the structure of the control system of the power converter in another embodiment;

[0047] FIG. 6 is a schematic diagram of the control method of the power converter in another embodiment. DETAILED DESCRIPTION

[0048] The technical solutions in the embodiments of the present disclosure will be described clearly and completely below with reference to the drawings in the embodiments of the present disclosure. Obviously, the described embodiments are only some of the embodiments of the present disclosure, not all. Based on the embodiments in the present disclosure, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present disclosure.

[0049] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. The terminology used in the description herein is for describing specific embodiments only and is not intended to be limiting of the disclosure.

[0050] It is to be understood that the terms “first”, “second”, and etc. can be used herein to describe various elements, but these elements are not limited by these terms. These terms are only used to distinguish a first element from another element. For example, a first resistor can be called a second resistor, and similarly, a second resistor can be called a first resistor, without departing from the scope of the disclosure.

[0051] It is to be understood that “connection” in the following embodiments, if the circuits, modules, units, etc. connected to each other have the transmission of electrical signals or data, should be understood as “electrically connected”, “communicatively connected” and the like.

[0052] It is to be understood that the term “based on” used in the disclosure is used to describe one or more factors that affect determination, and does not exclude other factors that can affect determination. For example, the phrase “determine A based on B” means that the determination of A can be based entirely or at least partially on factor B, that is, B is one of the factors affecting the determination of A, but does not exclude that the determination of A is also based on C.

[0053] As used herein, the singular forms “a”, “an” and “the” also include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “comprise / comprising” or “have / having” or etc. specifies the presence of stated features, integers, steps, operations, components, parts, or combinations thereof, but does not exclude the presence or addition of one or more other features, integers, steps, operations, components, parts, or combinations thereof. Meanwhile, the term “and / or” used in the specification includes any and all combinations of the related listed items.

[0054] During the operation of the power grid, the voltage and frequency may fluctuate due to load changes, generator set fluctuations, faults, etc. Among them, the grid voltage may rise or fall due to load changes or faults, causing voltage fluctuations; if the imbalance between power generation and load occurs, it may cause fluctuations in the frequency of the power grid; short circuit, switch action, etc. may also cause voltage sag or voltage interruption, and then cause transient fluctuations in the voltage of the power grid. The control system of the power converter relies on a phase-locked loop (PLL) to synchronize the frequency and phase of the grid voltage. When the grid frequency fluctuates greatly or the voltage is interrupted, the PLL may lose lock, causing the output voltage frequency to be out of sync, and then causing the control system to be chaotic. At the same time, when the grid voltage changes suddenly, the current control loop of the power converter may not be able to adjust in time, causing a sudden increase in current or overcurrent, resulting in equipment damage. In addition, when the power grid fluctuates, the power converter will have difficulty maintaining a stable output voltage and frequency, which may cause an increase in harmonics, voltage distortion, and other problems, affecting power quality.

[0055] The traditional power grid protection mechanism mainly determines whether to perform a protection action based on long-term changes in power grid parameters. However, voltage and frequency fluctuations may occur in a very short time, and the traditional protection mechanism has a slow response speed and a lagging reaction, which may cause the power converter to have entered an unstable state when the power grid is temporarily fluctuating, and the protection action has not yet been triggered. Therefore, in the case of transient power grid fluctuations, the power converter is likely to be damaged before the protection mechanism takes effect.

[0056] To solve the above problems, the embodiments of the present disclosure provide a control method of a power converter. The execution subject of the method can be a control system of the power converter. The power converter can be used to convert one form of electrical energy into another form of electrical energy, and can be an inverter, a rectifier, an AC / DC converter, etc. In a photovoltaic power generation system or a microgrid, the power converter can be an inverter, which is used to convert direct current into alternating current in order to be connected to the grid or to supply power to the load. In the embodiments of the present disclosure, the power converter is taken as a micro-inverter in a photovoltaic power generation system as an example, and other cases are similar, and necessary places will be described. The control system can be used to control the switching devices (such as MOSFET or IGBT) of the power converter, generate PWM (pulse width modulation) signals to adjust the working state of the power converter, and also be used to monitor the state of the photovoltaic power generation system or the microgrid, identify abnormal states and take measures. In addition, depending on the system design and application needs, the control system of the power converter can be both a part of the power converter, i.e. directly integrated inside the power converter, and an external system independent of the power converter.

[0057] In one embodiment, referring to FIG. 1, the power conversion circuit topology involved in the control method of the power converter provided by the embodiment of the present application is a single-stage isolated power conversion circuit topology. As shown in FIG. 1, the power conversion circuit includes a conversion circuit on the DC side and a bidirectional switch half-bridge circuit on the AC side, where DC represents the DC side power supply and AC represents the AC side power grid; the conversion circuit on the DC side adopts a full-bridge circuit form, the first bridge arm circuit of the conversion circuit on the DC side includes switch devices Q1 and Q2, and the second bridge arm circuit includes switch devices Q3 and Q4, where A and B are the load interfaces of the conversion circuit, and Tr is a transformer. The upper bridge arm circuit of the bidirectional switch circuit on the AC side is realized based on the bidirectional switch composed of switch devices Q5 and Q6, the lower bridge arm circuit is realized based on the bidirectional switch composed of switch devices Q7 and Q8, the bridge arm midpoint C is connected to the leakage inductance Lr of the converter, the upper bridge arm circuit corresponds to the capacitor Cp, the lower bridge arm circuit corresponds to the capacitor Cn, the capacitor Cp and the capacitor Cn are connected in series, the capacitor Co and the resistor Zg form a filter circuit; the leakage inductance Lr, the capacitor Cp and the capacitor Cn constitute a resonant circuit of the power conversion circuit, and provide a resonant current for the switching of the switch devices.

[0058] In other embodiments, the resonant circuit of the single-stage isolated power conversion topology can also be arranged on the DC side.

[0059] In one embodiment, referring to FIG. 2, the power conversion circuit topology involved in the control method of the power converter provided by the embodiment of the present application is a 1.5-level isolated power conversion circuit topology including a line-commutated circuit. As shown in FIG. 2, the 1.5-level isolated power conversion circuit includes a conversion circuit on the DC side, a transformer Ts, and a high-frequency conversion circuit and a line-commutated circuit on the AC side; in the case where the power transmission direction of the power converter is DC to AC, the high-frequency conversion circuit on the AC side converts the high-frequency AC current output by the AC side winding of the transformer Ts into a pulsating current with a period of half a line frequency period, and the line-commutated circuit flips the pulsating current into an AC current input to the power grid. The conversion circuit on the DC side adopts a full-bridge circuit form, the first bridge arm circuit of the conversion circuit on the DC side includes a switching device Q9 and a switching device Q10, and the second bridge arm circuit includes a switching device Q11 and a switching device Q12; A point and B point are the load interfaces of the conversion circuit on the DC side, Ts is a transformer; the conversion circuit on the DC side is connected in parallel with a DC bus capacitor C1, and the DC bus capacitor C1 is connected in parallel with a DC power supply device DC. The high-frequency conversion circuit on the AC side includes a switching device Q13, a switching device Q14, a switching device Q15, and a switching device Q16, wherein the source electrode of the switching device Q13 and the drain electrode of the switching device Q14 are connected, the source electrode of the switching device Q15 and the drain electrode of the switching device Q16 are connected, the source electrode of the switching device Q13 and the source electrode of the switching device Q15 are connected to a resonant inductor L1 (also a built-in leakage inductor of the transformer Ts) and a resonant capacitor C2, the source electrode of the switching device Q14 and the source electrode of the switching device Q8 are connected, and are commonly connected to the negative electrode of a filter capacitor C3; the drain electrode of the switching device Q13 and the drain electrode of the switching device Q15 are connected to the positive electrode of the filter capacitor C3. The line-commutated circuit includes a switching device Q17, a switching device Q18, a switching device Q19, and a switching device Q20, wherein the source electrode of the switching device Q17 and the drain electrode of the switching device Q18 are connected, the source electrode of the switching device Q19 and the drain electrode of the switching device Q20 are connected, the source electrode of the switching device Q17 and the source electrode of the switching device Q18 are connected, and are connected together with the source electrode of the switching device Q19 and the source electrode of the switching device Q20, and are commonly connected to the negative electrode of the filter capacitor C3. The first end of the line-commutated circuit is connected in parallel with the filter capacitor C3, and the second end of the line-commutated circuit is connected to the power grid through a common-mode inductor L2. The resonant inductor L1 and the resonant capacitor C2 on the AC side form a resonant circuit of the power conversion circuit, and provide a resonant current for switching of the switching devices.

[0060] In other embodiments, the high-frequency conversion circuit in the 1.5-level isolated power conversion circuit topology can also be implemented by a half-bridge circuit, and the switching device Q15 and the switching device Q16 are replaced by bridge arm capacitors respectively; in this embodiment, the resonant capacitor C2 shown in FIG. 2 can not be provided, and the bridge arm capacitors can be used as resonant capacitors to form a resonant circuit of the power conversion circuit together with the resonant inductor L1.

[0061] In other embodiments, the resonant circuit in the 1.5-stage isolated power conversion circuit topology can also be arranged at the DC side.

[0062] In one embodiment, the control method of the power converter provided by the embodiments of the present application involves a two-stage isolated power conversion circuit topology; the circuit topology is similar to the 1.5-stage isolated power conversion circuit topology shown in FIG. 2, and the high-frequency AC conversion circuit converts the high-frequency AC current output by the AC side winding of the transformer Ts into DC current, and the full-bridge circuit composed of the switching devices Q17 to Q20 is used to convert the DC current into power-frequency AC current.

[0063] In one embodiment, as shown in FIG. 3, a control method of a power converter is provided, comprising the following steps:

[0064] Step 301: periodically acquiring a real-time grid voltage according to a first preset time length.

[0065] In implementation, the control system of the power converter can be provided with an acquisition module, which can include various sensors (current sensor, voltage sensor, temperature sensor, etc.) for acquiring real-time state signals of the power converter and / or the grid. The control system can periodically sample the real-time grid voltage through the acquisition module, and the sampling interval time length can be the first preset time length, which can be a sampling interval time length preset according to control needs.

[0066] Step 302: if the acquired first real-time grid voltage is not within a preset voltage threshold range, controlling the power converter to enter a blocking standby state from a normal power generation state.

[0067] The voltage threshold range can be a voltage value range preset according to grid parameters, which can be used to determine whether a disturbance or power failure occurs in the grid. The first real-time grid voltage can be a real-time grid voltage sampled at any time.

[0068] In implementation, the control system of the power converter can be pre-configured with the above-mentioned voltage threshold range for evaluating whether the periodically sampled grid real-time voltage is normal. If the first grid real-time voltage sampled at a certain moment is not within the preset voltage threshold range, which can be higher than the upper limit of the voltage threshold range or lower than the lower limit of the voltage threshold range, it can be determined that the grid voltage is abnormal, so that the power converter can be controlled to enter the blocking standby state from the normal power generation state. Here, the normal power generation state is the normal operation state of the power converter. For the micro inverter, the micro inverter will convert the direct current output by the photovoltaic panel into alternating current according to the PWM control signal and transmit it to the grid at this time; the blocking standby state is a protection mode of the power converter, which is used to prevent abnormal voltage from causing equipment damage. For the micro inverter, the micro inverter suspends output of power to the grid at this time and is in standby or current limiting protection mode, i.e. in the blocking standby state, and decides whether to resume power generation or shut down according to subsequent control instructions.

[0069] Step 303, when the power converter is in the blocking standby state, the duration that the grid real-time voltage is within the voltage threshold range is obtained.

[0070] In implementation, after the power converter enters the blocking standby state in response to the control instruction, the control system can continue to periodically collect the grid real-time voltage and determine whether the grid real-time voltage is within the preset voltage threshold range, i.e. monitor whether the grid voltage has returned to normal. At the same time, the control system can record the duration that the grid real-time voltage is within the voltage threshold range through a timer. It can be understood that when the power converter enters the blocking standby state, the timer starts when the grid real-time voltage is first detected to be within the voltage threshold range. If the grid real-time voltage detected again is still within the voltage threshold range, the timer continues to count and accumulates the duration. If the grid real-time voltage detected again is not within the voltage threshold range, the timer starts again and the accumulated duration is cleared.

[0071] Step 304, when the duration is not less than a second preset duration, the power converter is controlled to enter the normal power generation state.

[0072] The second preset duration can be an interval duration preset according to actual operation needs for the power converter to resume operation from standby after the grid returns to normal.

[0073] In implementation, after it is detected that the grid real-time voltage is stable for more than the second preset duration (i.e. continuously within the voltage threshold range), the control system can control the power converter to switch back to the normal power generation state from the blocking standby state. For the micro inverter, the micro inverter can resume normal operation at this time and reconvert the direct current output by the photovoltaic panel into alternating current and transmit it to the grid.

[0074] The control method of the power converter disclosed in the present disclosure periodically samples the real-time grid voltage, when the real-time grid voltage is abnormal, controls the power converter to enter the blocking standby state, and after the real-time grid voltage returns to normal and lasts for a period of time, controls the power converter to enter the normal power generation state. In this way, by periodically sampling the grid voltage, real-time monitoring of the change of the grid voltage is realized, so that the power converter can be switched to the standby state in time under abnormal grid conditions, and the risk of damage to components can be avoided. Through the mechanism of continuous monitoring and timing, after the grid returns to normal, the power converter can resume power generation in time, improve energy utilization efficiency, and also avoid frequent switching of the working state of the power converter due to short-term fluctuations of the grid, which helps to prolong the service life of the equipment.

[0075] In one embodiment, as shown in FIG. 4, the control system of the power converter can at least include a main controller and a CPLD (Complex Programmable Logic Device), and the main controller can be an MCU, a DSP, an FPGA, etc., used to manage the workflow of the entire power converter, execute control algorithms, and coordinate various modules in the control system. In the embodiment of the present disclosure, an MCU is selected as the main controller, and other cases are similar, which will not be described in detail. During the operation of the control system, the main controller can generate PWM control parameters according to the collected current, voltage, power and other signals, and then send the PWM control parameters to the CPLD through the communication link between the main controller and the CPLD. The CPLD can receive the PWM control parameters transmitted by the main controller, quickly generate PWM signals to control the conduction and turn-off of the switching device, thereby affecting the output voltage and current of the power converter. Since the CPLD is a hardware logic device, its processing speed is very fast and can respond in nanoseconds, and it can generate high-precision control signals in a shorter time. As can be seen, the main controller is mainly responsible for high-level control decision and parameter operation, and the CPLD is responsible for executing real-time control logic. Using this architecture can effectively improve the response speed of the control system, so that the power converter can realize efficient and stable power conversion. Further, the state switching process of the power converter in the foregoing steps 302 and 304 can be realized by the MCU sending control instructions to the CPLD. That is, after the MCU sends a blocking instruction to the CPLD, the CPLD can enter a blocking current limiting state and pause sending PWM control signals to the power converter, so that the power converter enters the blocking standby state; after the MCU sends a wave generation instruction to the CPLD, the CPLD can enter a normal wave generation state and continuously send PWM control signals to the power converter, so that the power converter enters the normal power generation state.

[0076] In one embodiment, as shown in FIG. 5, the control system of the power converter includes a main controller. During the operation of the control system, the main controller can generate PWM signals according to the collected current, voltage, power and other signals, and directly send the PWM signals to the switching devices to control the turn-on and turn-off of the switching devices, thereby affecting the output voltage and current of the power converter.

[0077] In one embodiment, the sampling interval (first preset time length) of the real-time grid voltage can be determined by the maximum interrupt frequency of the main controller. The interrupt frequency of the main controller refers to the maximum frequency of interrupt signals that the main controller can process, i.e., the number of times the main controller can respond to interrupt requests per unit time. The maximum interrupt frequency of the main controller is affected by its clock frequency and interrupt processing time. The clock frequency is the speed at which the main controller executes instructions, and the interrupt processing time is the time the main controller takes to perform interrupt processing each time it responds to an interrupt. Interrupt processing can include saving the current state, executing interrupt tasks, and restoring the state. The higher the complexity of processing, the longer the time it takes. Specifically, if the maximum interrupt frequency of the main controller is 40 kHz, the sampling frequency of the grid real-time voltage can be 40 kHz, and the first preset time length can be 25 microseconds. In this way, setting the sampling frequency of the grid voltage according to the maximum interrupt frequency of the main controller can enable the main controller to process the change information of the grid voltage in a timely manner and control as needed, thereby ensuring the real-time response capability of the control system, especially in the case of abnormal grid, the control system can respond in time to protect the power converter. For example, in the case of grid disconnection, the grid voltage changes abruptly within tens of microseconds, while the response time of existing grid-related protection is more than tens of milliseconds, which cannot protect the power converter in time. The power converter will work in the case of abnormal grid voltage, which can easily lead to internal control disorder of the equipment, resulting in power tube through, and further failure or overcurrent. The control method of the present embodiment can protect the power converter in time to reduce the risk of failure or overcurrent.

[0078] In one embodiment, the second preset time length can be determined by the grid frequency. The grid frequency is the fluctuation frequency of alternating current in the grid, which represents the number of periodic changes of the grid voltage per unit time. The grid frequency can be 50 Hz, and the grid voltage changes 50 times per second. Each AC cycle of the grid lasts for 20 ms. The second preset time length is used to detect the time interval for the grid voltage to recover to stability. Associating the second preset time length with the grid frequency can make the judgment of grid recovery to stability more accurate and effective.

[0079] Specifically, considering that the grid voltage can fluctuate in a short time, selecting a short duration can cause misjudgment that the grid has stabilized, while the grid frequency is actually changing, which can cause the power converter to frequently switch between the power generation state and the blocking standby state, not only increasing the burden of the control system, but also possibly having a negative impact on the service life of the power converter. Therefore, the second preset duration can be set to be at least greater than one time of the duration of the AC cycle of the grid, which can ensure that at least one complete AC cycle is crossed to detect the change of the grid voltage, so as to avoid misjudgment of the stable state of the grid due to short-time voltage fluctuation. On the other hand, if the second preset duration is too large, although it can be more stable to judge whether the grid is stable, it can cause unnecessary delay of the control system after the grid recovers to be stable, and the power converter needs to wait for a long time to resume power generation, which affects the utilization efficiency of energy and the dynamic response ability of the control system. Therefore, the second preset duration can be selected to be less than two times of the duration of the AC cycle of the grid, to ensure the accuracy of judgment while reducing unnecessary waiting time.

[0080] For example, when the duration of the AC cycle of the grid is 20 ms, the second preset duration can be set to 30 ms. In the related art, when the grid triggers the power converter to stop working due to some small fluctuations caused by the access of some household appliances, the working efficiency of the power converter is extremely low. The control method of the embodiment can avoid the power converter from directly stopping working due to small fluctuations, not only improving the working efficiency of the power converter in the case of a small amount of small fluctuations, but also being able to perform blocking protection in the case of a large amount of small fluctuations of the grid.

[0081] In the power converter involved in the embodiment, a resonance circuit is arranged in the conversion circuit of the power converter. When the conversion circuit is blocked, some energy remains in the resonance capacitor and the resonance inductor and needs to be released to avoid causing inrush current when restarting work. If the second preset duration is set to be relatively short, such as tens of us (microseconds) or hundreds of us, the residual energy in the resonance circuit can not be completely discharged, and the work needs to be restarted. In the embodiment, the second preset duration is set to be in the order of milliseconds, especially more than 20 ms, which can ensure that the residual energy in the resonance capacitor and the resonance inductor is completely released after the switching device is blocked, and improve the stability and reliability of the power converter.

[0082] The switching frequency of the switching tube in the conversion circuit of the power converter involved in the embodiments of the present application is very high, generally tens of KHz (kilohertz) to hundreds of KHz, and a complete switching period is generally only tens of microseconds. If the second preset time length is set at the microsecond level, the main controller can not be able to process the control logic such as fault detection, clamp command generation, recovery detection and recovery command generation in such a short time, resulting in low control reliability. In the embodiments, the second preset time length is set at the millisecond level, especially more than 20 ms, so that the main controller has sufficient time to execute the related control logic and improve the reliability of the control.

[0083] In view of the above various conditions, the applicant has made a large number of experiments and made trade-offs according to different requirements, and finally determined that the second preset time length should be selected between 1 and 2 times of the AC period of the power grid, for example, in a 50 Hz power grid environment (period 20 ms), about 30 ms is a relatively optimal solution. This setting can effectively avoid misjudgment caused by short-time voltage fluctuation, avoid frequent start and stop of power devices, ensure sufficient discharge of residual energy and reliable execution of control logic, and restart in time after the power grid is restored, taking into account system reliability, response speed and energy utilization efficiency.

[0084] In one embodiment, after a relatively long time of experiencing the clamping standby, the power converter can enter a shutdown state, i.e., after step 303, step 305 can exist as shown in FIG. 6: if the power converter continues to be in the clamping standby state for a time length greater than a third preset time length, the power converter enters a shutdown state.

[0085] The third preset time length can be a preset safety time limit for indicating the maximum time that the power converter can remain in the clamping standby state. If the power converter continues to operate in the clamping standby state for more than the third preset time length, it indicates that the power grid can have long-term instability or serious abnormalities and cannot be restored to a normal power generation state in a short time. Specifically, when the AC period of the power grid is 20 ms, the third preset time length can be selected as 10 seconds.

[0086] In implementation, after entering the envelope standby state, the power converter can start timing and record the duration of staying in the state, and if the duration is greater than a third preset duration, the power converter can enter the shutdown state from the envelope standby state. It can be understood that the control system in the envelope standby state will still maintain the basic circuit operation and will produce a certain degree of energy consumption. Especially when the power grid cannot be restored for a long time, it is meaningless to continue to maintain the envelope standby state, so it can enter the shutdown state to completely cut off the power supply, save energy, and prolong the service life of the equipment. It is worth mentioning that if the control system is integrated inside the power converter, the entire device (including the control system) will stop working in the shutdown state, so the monitoring function of the real-time voltage of the power grid will also be closed, and when the power grid returns to normal and is awakened by an external signal or manually intervened by a technician, the power converter can be restarted; and if the control system is external, even if the power converter enters the shutdown state, the monitoring function of the real-time voltage of the power grid can still continue, and the control system can continue to determine whether to restart the power converter by monitoring the state of the power grid, so that the power converter can automatically resume work after the power grid returns to normal, without manual intervention.

[0087] In one embodiment, the voltage threshold range can be determined by the real-time voltage of the power grid in the historical period, and accordingly, there can be a process as follows: determining the voltage threshold range corresponding to the current alternating cycle of the power grid according to the real-time voltage of the power grid obtained in the alternating cycle of the power grid history.

[0088] Among them, the alternating cycle of the power grid history refers to one or more alternating cycles experienced in the past period of time, and the total duration can be several seconds, several minutes, etc. Optionally, 50 alternating cycles can be selected, that is, when the alternating cycle is 20 ms, the total duration can be selected as 1 s.

[0089] In implementation, in each alternating cycle, the control system samples the real-time voltage of the power grid, and can store the real-time voltage corresponding to the sampling time. When determining the voltage threshold range, the voltage threshold range of each alternating cycle can be set in units of each alternating cycle of the power grid. Further, the control system can obtain the voltage threshold range of the current alternating cycle by analyzing the historical voltage data of the power grid, that is, analyze the change trend (such as fluctuation amplitude, frequency, etc.) of the real-time voltage of the power grid in the historical multiple alternating cycles, and dynamically adjust the voltage threshold range. Of course, the selected historical alternating cycles can be adjacent to multiple continuous alternating cycles, or multiple alternating cycles with intervals, or alternating cycles excluding specific alternating cycles, etc. The specific selection can be determined according to the actual scene demand of the power grid. In this way, by statistical analysis of the past voltage fluctuation, the possible future voltage change situation can be estimated, the voltage threshold range can be more adapted to the dynamic change of the power grid, and thus unnecessary misjudgment of the power grid anomaly and state switching of the power converter can be reduced, and the stability and reliability of the power system are improved.

[0090] Specifically, the voltage threshold range corresponding to the current alternating cycle of the power grid includes the voltage threshold range corresponding to each time point in the current alternating cycle of the power grid; the voltage threshold range corresponding to each time point is a voltage interval with a preset voltage difference, and the middle value is obtained from the real-time voltage of the power grid in the historical N alternating cycles of the power grid.

[0091] In implementation, taking 20 ms as an example for the length of the alternating cycle of the power grid, the overall real-time voltage of the power grid fluctuates in a triangular function waveform in one alternating cycle. At different moments of the alternating cycle, the real-time voltage of the power grid assumes different values. Correspondingly, the voltage threshold range corresponding to each moment in one alternating cycle should also be set. For example, when the real-time voltage of the power grid is in the rising period, the overall value of the voltage threshold range corresponding to a moment can be relatively high. When the voltage is in the falling period, the overall value of the voltage threshold range corresponding to another moment can be relatively low. Further, the voltage threshold range can be in the form of a voltage interval, and the voltage interval can be defined based on a median value and a voltage difference. Here, the median value can be the central value of the voltage interval, and can also be understood as the reference voltage of the voltage fluctuation. The median value can be calculated according to the real-time voltage of the power grid in the historical N alternating cycles of the power grid. If the voltage at some moments in the historical alternating cycles is usually high, the median value at the moment in the current alternating cycle will also be increased accordingly. Conversely, it will be decreased. The preset voltage difference is the span of the voltage threshold range, that is, the allowed voltage fluctuation range. If the fluctuation of the real-time voltage of the power grid does not exceed the voltage fluctuation range, the normal operation of the power converter is not affected, otherwise the voltage protection for the power converter will be triggered. The specific value of the preset voltage difference can be set according to the voltage fluctuation of the power system, the effective value of the power grid voltage, and the device performance of the power converter, etc. In this way, by referring to the voltage fluctuation in the historical alternating cycles, the voltage threshold at each moment in the current alternating cycle is dynamically adjusted, the median value is set using the historical data, and the preset voltage difference is added to tolerate a certain degree of voltage fluctuation without easily triggering the protection mechanism. This not only improves the adaptability to the power grid fluctuation, but also avoids frequent entry into standby or shutdown state, thereby improving the operation efficiency of the power converter.

[0092] It should be understood that, although each step in the flowchart involved in the above embodiments is shown in sequence according to the arrow, these steps are not necessarily executed in sequence according to the arrow. Unless otherwise specified herein, the execution of these steps is not strictly limited in sequence, and these steps can be executed in other sequences. Moreover, at least part of the steps in the flowchart involved in the above embodiments can include multiple steps or stages, which are not necessarily executed at the same time, but can be executed at different times, and the execution sequence of these steps or stages is not necessarily sequential, but can be executed in rotation or alternation with at least part of other steps or stages.

[0093] Based on the same inventive concept, the disclosure also provides a control system of a power converter, the control system comprising a main controller, the main controller being configured to:

[0094] acquiring the real-time grid voltage periodically according to a first interval;

[0095] if the acquired first real-time grid voltage is not within a preset voltage threshold range, controlling the power converter to enter a blocking standby state from a normal power generation state;

[0096] when the power converter is in the blocking standby state, acquiring a duration that the real-time grid voltage is within the voltage threshold range;

[0097] when the duration is not less than a second preset duration, controlling the power converter to enter the normal power generation state.

[0098] In one embodiment, the control system further comprises a CPLD, and the main controller is configured to: if the acquired first real-time grid voltage is not within the preset voltage threshold range, control the CPLD to enter a blocking state from a wave generation state; when the CPLD is in the blocking state, acquire a duration that the real-time grid voltage is within the voltage threshold range; and when the duration is not less than the second preset duration, control the CPLD to enter the wave generation state.

[0099] In the embodiment, the main controller controls the power converter to enter the blocking standby state or the normal power generation state by controlling the CPLD to enter the blocking state and the wave generation state.

[0100] In one of the embodiments, the first preset duration is determined by a maximum interrupt frequency of the main controller.

[0101] In one of the embodiments, the second preset duration is determined by a grid frequency.

[0102] In one of the embodiments, the second preset duration is greater than one time of an AC cycle duration of the grid and less than two times of the AC cycle duration of the grid.

[0103] In one of the embodiments, if a duration that the power converter continuously stays in the blocking standby state is greater than a third preset duration, the power converter enters a shutdown state.

[0104] In one of the embodiments, the main controller is further configured to:

[0105] determining the voltage threshold range corresponding to a current AC cycle of the grid according to the real-time grid voltage acquired in the AC cycle of the grid history.

[0106] In one of the embodiments, the voltage threshold range corresponding to the current AC cycle of the grid comprises voltage threshold ranges corresponding to respective time points in the current AC cycle of the grid;

[0107] the voltage threshold range corresponding to each time point is a voltage interval with a preset voltage difference and a middle value obtained from the real-time grid voltage in N AC cycles of the grid history.

[0108] The embodiments of the present disclosure further provide a power converter, which comprises the control system.

[0109] In one embodiment, the power conversion circuit in the power converter adopts an isolated power conversion circuit comprising a resonance circuit.

[0110] In one embodiment, the isolated power conversion circuit is a single-stage isolated power conversion circuit or a 1.5-stage isolated power conversion circuit or a two-stage isolated power conversion circuit.

[0111] The embodiments of the present disclosure further provide a chip comprising a memory and a processor, wherein the memory stores a computer program, and the processor implements the steps in the above-mentioned method embodiments when executing the computer program.

[0112] In one embodiment, a computer readable storage medium is provided, which stores a computer program, and the computer program is executed by a processor to implement the steps in the above-mentioned method embodiments.

[0113] In one embodiment, a computer program product is provided, which comprises a computer program, and the computer program is executed by a processor to implement the steps in the above-mentioned method embodiments.

[0114] It should be noted that the user information (including but not limited to user equipment information, user personal information, etc.) and data (including but not limited to data for analysis, stored data, displayed data, etc.) involved in the present disclosure are all information and data authorized by the user or authorized by all parties, and the collection, use and processing of the related data need to comply with relevant regulations.

[0115] Those skilled in the art can understand that all or part of the processes in the above-mentioned embodiment methods can be completed by instructing the relevant hardware through a computer program. The computer program can be stored in a non-volatile computer readable storage medium, and when executed, can include the processes of the above-mentioned embodiment methods. Any reference to memory, database or other medium used in the embodiments provided by the present disclosure can include at least one of non-volatile and volatile memory. Non-volatile memory can include read-only memory (ROM), magnetic tape, floppy disk, flash memory, optical storage, high-density embedded non-volatile memory, resistive memory (ReRAM), magnetoresistive random access memory (MRAM), ferroelectric memory (FRAM), phase change memory (PCM), graphene memory, etc. Volatile memory can include random access memory (RAM) or external cache memory, etc. As an illustration but not limitation, RAM can be in various forms, such as static random access memory (SRAM) or dynamic random access memory (DRAM), etc. The processor involved in the embodiments provided by the present disclosure can be a general-purpose processor, a central processing unit, a graphics processing unit, a digital signal processor, a programmable logic device, a quantum computing-based data processing logic device, etc., without being limited thereto.

[0116] Any combination of the technical features of the above-mentioned embodiments can be made, and in order to make the description simple, all possible combinations of the technical features in the above-mentioned embodiments are not described, however, as long as the combination of the technical features does not exist contradictory, it should be considered as the scope of the present disclosure.

[0117] The above-mentioned embodiments only express several implementation manners of the present disclosure, and the description is more specific and detailed, but it should not be understood as a limitation on the scope of the patent application. It should be noted that for those skilled in the art, without departing from the concept of the present disclosure, a number of modifications and improvements can be made, which are all within the protection scope of the present disclosure. Therefore, the protection scope of the present disclosure patent should be subject to the appended claims.

Claims

1. A control method of a power converter, wherein, The control method comprises: periodically acquiring real-time grid voltage according to a first preset time length; if the acquired first real-time grid voltage is not within a preset voltage threshold range, controlling the power converter to enter a wave blocking standby state from a normal power generation state; when the power converter is in the wave blocking standby state, acquiring a duration that the real-time grid voltage is within the voltage threshold range; when the duration is not less than a second preset time length, controlling the power converter to enter the normal power generation state.

2. The control method according to claim 1, wherein The control method is applied to a control system of a power converter, and the control system at least comprises a main controller and a CPLD; The control method is implemented by the main controller; The CPLD is used to enter a wave emitting state or a wave blocking state in response to a control instruction of the main controller, so that the power converter enters the normal power generation state or the wave blocking standby state.

3. The control method according to any one of claims 1-2, wherein, The first preset time length is determined by a maximum interrupt frequency of the main controller.

4. The control method according to any one of claims 1 to 3, wherein The second preset time length is determined by a grid frequency.

5. The control method according to any one of claims 1 to 4, wherein The second preset time length is greater than one time length of an alternating current cycle of the grid and less than two time lengths of the alternating current cycle of the grid.

6. The control method according to any one of claims 1 to 5, wherein The control method further comprises: if a duration that the power converter continuously stays in the wave blocking standby state is greater than a third preset time length, the power converter enters a shutdown state.

7. The control method according to any one of claims 1-6, wherein, After the periodically acquiring real-time grid voltage according to a first preset time length, the control method further comprises: determining a voltage threshold range corresponding to a current alternating current cycle of the grid according to real-time grid voltages acquired in the alternating current cycle of the grid in history.

8. The control method according to claim 7, wherein The voltage threshold range corresponding to the current alternating current cycle of the grid comprises voltage threshold ranges corresponding to respective time points in the current alternating current cycle of the grid; the voltage threshold range corresponding to each time point is a voltage interval with a preset voltage difference, and a middle value of the voltage interval is obtained from real-time grid voltages in N alternating current cycles of the grid in history.

9. The method according to any one of claims 1 to 8, characterized in that, The power conversion circuit in the power converter adopts an isolation type power conversion circuit comprising a resonance circuit.

10. The method of claim 9, wherein, The isolation type power conversion circuit is a single-stage isolation type power conversion circuit, a 1.5-stage isolation type power conversion circuit, or a two-stage isolation type power conversion circuit.

11. A control system for a power converter, wherein, The control system comprises a main controller, and the main controller is used to: periodically acquire real-time grid voltage according to a first preset time length; if the acquired first real-time grid voltage is not within a preset voltage threshold range, control the power converter to enter a wave blocking standby state from a normal power generation state; when the power converter is in the wave blocking standby state, acquire a duration that the real-time grid voltage is within the voltage threshold range; when the duration is not less than a second preset time length, control the power converter to enter the normal power generation state.

12. The control system of claim 11, wherein, The control system further comprises a CPLD, and the main controller is used to: if the acquired first real-time grid voltage is not within a preset voltage threshold range, control the CPLD to enter a wave blocking state from a wave emitting state; when the CPLD is in the wave blocking state, acquire a duration that the real-time grid voltage is within the voltage threshold range; when the duration is not less than a second preset time length, control the CPLD to enter the wave emitting state.

13. A power converter, wherein, The power converter includes the control system according to claim 11 or 12.

14. The power converter of claim 13, wherein, The power conversion circuit in the power converter is an isolated power conversion circuit including a resonance circuit.

15. The power converter of claim 14, wherein, The isolated power conversion circuit is a single-stage isolated power conversion circuit, a 1.5-stage isolated power conversion circuit, or a two-stage isolated power conversion circuit.

16. A chip comprising a memory and a processor, the memory storing a computer program, wherein, The processor, when executing the computer program, implements the steps of the control method of the power converter according to any one of claims 1-10.

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